Phonon modulated switching devices are known, and are described in U.S. Pat. No. 5,374,831 entitled Quantum Well Phonon Modulator in the names of Mitra Dutta, et al., which is assigned to the assignee of the present invention and which is incorporated herein by reference. As disclosed in that patent, optical phonon emission from a first quantum well provides a scattering mechanism for electrons in an adjacent well, to reduce the current in the adjacent well.